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Osmoregulation and Excretion CHAPTER 44 CHAPTER 44

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Page 1: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Osmoregulation and Excretion

CHAPTER 44CHAPTER 44

Page 2: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

WATER BALANCE

Osmolarity - total solute Osmolarity - total solute concentration (M) = moles of concentration (M) = moles of solute per litersolute per liter

Osmosis – water moves from Osmosis – water moves from hypoosmotic (less solute) to hypoosmotic (less solute) to hyperosmotic (greater solute)hyperosmotic (greater solute)

Page 3: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Figure 44.12 Salt-excreting glands in birds

Page 4: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Figure 44.14a Osmoregulation in a saltwater fish

Page 5: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Figure 44.14b Osmoregulation in a freshwater fish

Page 6: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

OsmoconformerOsmoconformer - does not - does not actively adjust internal osmolarityactively adjust internal osmolaritySome saltwater fish, most Some saltwater fish, most

marine invertebratesmarine invertebrates

Page 7: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

OsmoregulatorOsmoregulator – adjusts – adjusts internal osmolarityinternal osmolarityAll freshwater fish, some All freshwater fish, some

mammals, most marine mammals, most marine vertebratesvertebrates

Cost of regulation depends on Cost of regulation depends on environmentenvironment

Page 8: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

AnhydrobiosisAnhydrobiosis – a few animals – a few animals can lose almost all of their body can lose almost all of their body water and survive in a dormant water and survive in a dormant statestateTardigrades (water bears)Tardigrades (water bears)Some nematodesSome nematodes

DesiccationDesiccation Humans die if lose 12% body Humans die if lose 12% body

waterwater

Page 9: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Figure 44.15 Anhydrobiosis: Hydrated tardigrade (left), dehydrated tardigrade (right)

Page 10: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

EXCRETORY SYSTEMS

Balancing water loss and gains and Balancing water loss and gains and disposing of wastesdisposing of wastes

Transport epitheliumTransport epithelium – layer(s) of – layer(s) of epithelial cells the regulate solute epithelial cells the regulate solute movement (selectively permeable movement (selectively permeable membranes)membranes)

Most harmful wastes are Most harmful wastes are nitrogen nitrogen products from breakdown of proteins products from breakdown of proteins and nucleic acidsand nucleic acids

Page 11: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Figure 44.16 Water balance in two terrestrial mammals

Page 12: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Figure 44.13 Nitrogenous wastes

Page 13: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

AMMONIA

Most waste is NHMost waste is NH33

Most aquatic animals secrete Most aquatic animals secrete nitrogenous wastes as nitrogenous wastes as ammonia or ammonium (NHammonia or ammonium (NH44

++))

Many animals convert NHMany animals convert NH33 to to

urea or uric acidurea or uric acid

Page 14: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

UREA

Mammals, most amphibians, Mammals, most amphibians, sharks, some fishessharks, some fishes

100,000 times less toxic than 100,000 times less toxic than NHNH33

Produced in vertebrate liver by Produced in vertebrate liver by combining COcombining CO22 with NH with NH33

Urea is carried to kidneysUrea is carried to kidneys

Page 15: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

URIC ACID

Land snails, birds, insects, many Land snails, birds, insects, many reptilesreptiles

Least soluble in waterLeast soluble in water Excreted in paste-like form so little Excreted in paste-like form so little

water losswater loss Can be stored within shelled egg Can be stored within shelled egg

without harming embryowithout harming embryo

Page 16: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Dispose wastesDispose wastes OverviewOverview

FiltrationFiltration – fluids filtered – fluids filtered through transport epitheliathrough transport epithelia

ReabsorptionReabsorption – some filtered – some filtered compounds are actively compounds are actively transported back to body fluidstransported back to body fluids

Secretion Secretion – removal of wastes – removal of wastes from bodyfrom body

Page 17: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Figure 44.17 Key functions of excretory systems: an overview

Page 18: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

PLATYHELMINTHES (FLATWORMS)

ProtonephridiumProtonephridium – network of – network of closed tubules throughout closed tubules throughout body; branches end in flame body; branches end in flame bulbsbulbs

Cilia provide movement of fluid Cilia provide movement of fluid within tubuleswithin tubules

Page 19: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Functions mostly in Functions mostly in osmoregulationosmoregulation

Most metabolic waste diffuse Most metabolic waste diffuse outout

Page 20: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Figure 44.18 Protonephridia: the flame-bulb system of a planarian

Page 21: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

ANNELIDS

MetanephridiumMetanephridium – tubular – tubular system with internal openings system with internal openings located in each segmentlocated in each segment

NephrostomeNephrostome – internal – internal opening where fluid entersopening where fluid enters

Page 22: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Most solutes reabsorbed into Most solutes reabsorbed into blood capillariesblood capillaries

Nitrogenous wastes exit via Nitrogenous wastes exit via nephridioporesnephridiopores

Page 23: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Figure 44.19 Metanephridia of an earthworm

Page 24: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

INSECTS AND TERRESTRIAL ARTHROPODS Malpighian tubulesMalpighian tubules – remove – remove

nitrogenous wastes from nitrogenous wastes from hemolymphhemolymph

Empties into digestive tract and Empties into digestive tract and is eliminated in fecesis eliminated in feces

Page 25: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Figure 44.20 Malpighian tubules of insects

Page 26: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

MAMMALIAN KIDNEY

Renal arteryRenal artery – blood enters – blood enters kidneykidney

Renal veinRenal vein – blood leave – blood leave kidneykidney

UreterUreter – tube that takes urine – tube that takes urine from kidney to bladderfrom kidney to bladder

Page 27: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Urinary bladderUrinary bladder – urine (from – urine (from ureters) is storedureters) is stored

UrethraUrethra – tube in which urine – tube in which urine leaves bladder and exits bodyleaves bladder and exits body

Page 28: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Renal cortexRenal cortex – outer region of – outer region of kidneykidney

Renal medullaRenal medulla – inner region of – inner region of kidneykidney

Renal pelvis Renal pelvis – area in center of – area in center of kidney where urine collectskidney where urine collects

NephronNephron – functional unit of kidney– functional unit of kidney GlomerulusGlomerulus – ball of capillaries of – ball of capillaries of

each nephroneach nephron Bowman’s CapsuleBowman’s Capsule – surrounds – surrounds

glomerulusglomerulus

Page 29: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Figure 44.21 The human excretory system at four size scales

Page 30: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Figure 44.22 The nephron and collecting duct: regional functions of the transport epithelium

Page 31: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

FILTRATION OF BLOOD

Blood pressure sends anything Blood pressure sends anything small enough into Bowman’s small enough into Bowman’s capsulecapsuleFiltrate includes glucose, Filtrate includes glucose,

salts, nitrogenous wastes, salts, nitrogenous wastes, vitamins, but vitamins, but notnot cells cells

Page 32: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Filtrate passes through 3 regions Filtrate passes through 3 regions of nephron:of nephron:Proximal tubuleProximal tubuleLoop of HenleLoop of HenleDistal tubuleDistal tubule

Filtrate (urine) Empties in Filtrate (urine) Empties in collecting ductcollecting duct

Urine then empties into renal Urine then empties into renal pelvispelvis

Urine leaves kidneys via uretersUrine leaves kidneys via ureters

Page 33: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Blood vessels along nephronsBlood vessels along nephronsAfferent arterioleAfferent arteriole – blood to – blood to

glomerulusglomerulusEfferent arterioleEfferent arteriole – blood – blood

away from glomerulusaway from glomerulusDivides in capillaries that Divides in capillaries that supply proximal and distal supply proximal and distal tubule and loop of Henletubule and loop of Henle

Page 34: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

SecretionSecretion – substances put – substances put into proximal and distal tubules into proximal and distal tubules from blood (selective process)from blood (selective process)

ReabsorptionReabsorption – substances – substances put back into bloodput back into bloodNearly all water, sugar, Nearly all water, sugar,

vitamins, and nutrients are vitamins, and nutrients are reabsorbedreabsorbed

Page 35: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Figure 44.23 How the human kidney concentrates urine: the two-solute model (Layer 1)

Page 36: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Figure 44.23 How the human kidney concentrates urine: the two-solute model (Layer 2)

Page 37: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Figure 44.23 How the human kidney concentrates urine: the two-solute model (Layer 3)

Page 38: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Filtration Proximal tubuleProximal tubule

HCOHCO33--, NaCl, H, NaCl, H22O, nutrients (ex. O, nutrients (ex.

glucose and amino acids), Kglucose and amino acids), K++ reabsorbed (some actively and some reabsorbed (some actively and some passively)passively)

HH++ and NH and NH33 secreted secreted Descending loop of HenleDescending loop of Henle

Cells permeable to water, but not Cells permeable to water, but not NaCl; water reabsorbed by osmosisNaCl; water reabsorbed by osmosis

Filtrate becomes more concentratedFiltrate becomes more concentrated

Page 39: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Ascending loop of HenleAscending loop of HenleCells permeable to NaCl, but not Cells permeable to NaCl, but not

water; NaCl reabsorbed by water; NaCl reabsorbed by passive and then active transportpassive and then active transport

Filtrate becomes more dilutedFiltrate becomes more diluted Distal TubuleDistal Tubule

HCOHCO33--, NaCl, and H, NaCl, and H22O reabsorbedO reabsorbed

HH++ and K and K++ secreted secreted

Page 40: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Collecting ductCollecting ductWater is reabsorbed passivelyWater is reabsorbed passivelyNaCl is actively reabsorbed (in outer NaCl is actively reabsorbed (in outer

medulla)medulla)Urea and HUrea and H22O are passively O are passively

reabsorbed (in inner medulla)reabsorbed (in inner medulla)Urine becomes more concentratedUrine becomes more concentrated

Page 41: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Making urine in humans

Approximately 1600 L of blood flows Approximately 1600 L of blood flows through a pair of kidneys and we make through a pair of kidneys and we make approximately 1.5 L of urine per dayapproximately 1.5 L of urine per day

Osmolarity of blood is about 300 Osmolarity of blood is about 300 mOsm/L and osmolarity of urine is mOsm/L and osmolarity of urine is about 1200 mOsm/Labout 1200 mOsm/L

Kidneys are water-conserving (involves Kidneys are water-conserving (involves lots of energy to move solutes actively)lots of energy to move solutes actively)

Page 42: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

HORMONAL FEEDBACK

Hormones link kidney function, water Hormones link kidney function, water balance, and blood pressurebalance, and blood pressure

Antidiuretic hormone (ADH)Antidiuretic hormone (ADH)Made in hypothalamus and stored in Made in hypothalamus and stored in

pituitary glandpituitary glandSecreted when blood osmolarity risesSecreted when blood osmolarity risesMay be caused by excessive May be caused by excessive

sweating, diarrhea, or eating salty sweating, diarrhea, or eating salty foodsfoods

Page 43: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Increases water reabsorption in Increases water reabsorption in distal tubule and collecting duct distal tubule and collecting duct (makes membranes more (makes membranes more permeable to water)permeable to water)

Alcohol can inhibit ADH so Alcohol can inhibit ADH so excessive drinking causes excessive drinking causes dehydration (due to excessive dehydration (due to excessive urination)urination)

Page 44: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute
Page 45: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute
Page 46: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

RAAS system of regulationRAAS system of regulation Juxtaglomerular apparatusJuxtaglomerular apparatus

Specialized tissue located near Specialized tissue located near afferent arteriole which supplies afferent arteriole which supplies blood to glomerulusblood to glomerulus

Responds to low blood pressure Responds to low blood pressure by secreting by secreting reninrenin

ReninRenin activates activates angiotensinogenangiotensinogen which which becomes becomes angiotension IIangiotension II

Page 47: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Angiotension IIAngiotension II increase blood increase blood pressure by:pressure by:Constricting arteriesConstricting arteriesSignals proximal tube to reabsorb Signals proximal tube to reabsorb more NaCl and watermore NaCl and water

Stimulates Stimulates adrenal glandadrenal gland to to secrete secrete aldosteronealdosterone

AldosteroneAldosterone increases the increases the reabsorption of sodium and water reabsorption of sodium and water in distal tubes, which increases in distal tubes, which increases blood volume and pressureblood volume and pressure

Page 48: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute
Page 49: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Hypertension and Kidneys

Hypertension is treated with drugs that Hypertension is treated with drugs that inhibit angiotensin II.inhibit angiotensin II.

Many hypertension drugs inhibit the Many hypertension drugs inhibit the ACE enzyme that takes Angiotensin I ACE enzyme that takes Angiotensin I and cleaves it to make Angiotensin IIand cleaves it to make Angiotensin II

Page 50: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute
Page 51: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

DIVERSE ADAPTATIONS

Birds: shorter loops of Henle Birds: shorter loops of Henle so urine not as concentratedso urine not as concentrated

Freshwater fish: must Freshwater fish: must conserve salts so more conserve salts so more reabsorption of ionsreabsorption of ions

Page 52: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Marine fish – lack glomeruli and Marine fish – lack glomeruli and Bowman’s capsules so excrete Bowman’s capsules so excrete mostly divalent ions while gills mostly divalent ions while gills excrete monovalent ionsexcrete monovalent ions

Frogs: can reabsorb water from Frogs: can reabsorb water from bladderbladder

Page 53: Osmoregulation and Excretion CHAPTER 44. WATER BALANCE Osmolarity - total solute concentration (M) = moles of solute per liter Osmolarity - total solute

Figure 44.25 A vampire bat (Desmodus rotundas), a mammal with a unique excretory situation. While the bat feeds on a blood meal, its kidneys make dilute urine copiously. Thus shedding weight for the flight home. While the bat roosts during the day, the kidneys secrete small amounts of concentrated urine.